EP0796747B1 - Soft elastomeric material safety ring for tyre - Google Patents

Description

The present invention relates to safety supports for pneumatic tires. vehicles that are mounted inside the tires, on their rims, to resume charging in the event of tire failure. Particularly, it offers an improved support essentially made of a material flexible elastomer.

The use of an annular safety support, made of material flexible elastomer has been known for a long time. Such support presents the advantages of not being sensitive to shocks, of offering good stability of performance over time and not to degrade the characteristics of behavior of the tire in the event of rolling in support.

On the other hand, such support has two major shortcomings. Unacceptable weight matters given the current requirements of car manufacturers to reduce weight axles of their vehicles and very insufficient endurance when driving under support because of the heating of the material likely to cause a very rapid thermal degradation.

To resolve these faults, patent application FR 2,532,591 offers support mainly made of elastomeric material, symmetrical H-shaped relative to a longitudinal median plane with a wide circumferential groove in its radially lower part to lighten it and reduce its rigidity, the groove circumferential located in its radially outer part being a housing for a support retention strap on the rim. This support provides actually reduced weight and acceptable endurance, but at the cost of relatively high radial stiffness of the support since more than 750 kg / cm, this which affects the quality of the behavior of the tire when rolling in support.

• une base sensiblement cylindrique destinée à s'adapter autour de la jante,
• un sommet sensiblement cylindrique destiné à entrer en contact avec la bande de roulement en cas de perte de pression, et laissant une garde par rapport à celle-ci à la pression nominale, et
• un corps annulaire reliant ladite base et ledit sommet, formé par des éléments radiaux indépendants.

US patent A 4 248 286 describes a safety support intended to be mounted on a rim inside a tire fitted to a vehicle, to support the tread of this tire in the event of loss of inflation pressure, this support being essentially made of a flexible elastomeric material, and comprising:

• a substantially cylindrical base intended to fit around the rim,
• a substantially cylindrical crown intended to come into contact with the tread in the event of a loss of pressure, and leaving a clearance with respect to the latter at nominal pressure, and
• an annular body connecting said base and said vertex, formed by independent radial elements.

The invention relates to a safety support made of a material essentially flexible elastomer whose compromise between the performances of behavior, weight and endurance is significantly improved.

• une base sensiblement cylindrique destinée à s'adapter autour de la jante,
• un sommet sensiblement cylindrique destiné à entrer en contact avec la bande de roulement en cas de perte de pression, et laissant une garde par rapport à celle-ci à la pression nominale, et
• un corps annulaire reliant ladite base et ledit sommet.

Cet appui est caractérisé en ce que le corps présente une pluralité d'évidements de direction sensiblement axiale, débouchant dans la face du corps destinée à être placée du côté extérieur du véhicule et s'étendant axialement jusqu'au moins la moitié du corps sans le traverser.The safety support according to the invention is intended to be mounted on a rim inside a tire fitted to a vehicle, to support the tread of this tire in the event of loss of inflation pressure, this support is essentially made of a flexible elastomeric material, and comprises:

• a substantially cylindrical base intended to fit around the rim,
• a substantially cylindrical crown intended to come into contact with the tread in the event of a loss of pressure, and leaving a clearance with respect to the latter at nominal pressure, and
• an annular body connecting said base and said vertex.

This support is characterized in that the body has a plurality of recesses of substantially axial direction, opening into the face of the body intended to be placed on the outside of the vehicle and extending axially up to at least half of the body without the to cross.

Preferably, the annular body has the same axial width as the base.

• une première zone annulaire, massive, telle que, dans toute la gamme de charges radiales qu'elle est susceptible de subir en appui, elle s'oppose à ces charges radiales par des contraintes de compression sans flambement ; la rigidité en compression de cette zone est suffisante pour ne subir que des déformations de faible amplitude et donc des échauffements limités ;
• une seconde zone annulaire, disposée du côté extérieur du véhicule, comprenant les évidements transversaux ouverts sur le côté du corps annulaire ; cette zone est notablement plus souple que la précédente et permet ainsi le maintien d'une zone de contact importante sans cloquage entre le sommet de l'appui et la surface radialement intérieure du sommet du pneumatique et ainsi procure une aire de contact importante entre le sol et la surface de la bande de roulement du pneumatique lors du roulage en appui en s'opposant à tout cloquage éventuel de cette bande de roulement.

The transverse recesses of this support according to the invention allow a very strong reduction in the weight of the support relative to a full support and define two areas of the body of the support whose mechanical functioning is very different:

• a first annular zone, massive, such that, throughout the range of radial loads that it is likely to undergo in support, it opposes these radial loads by compression stresses without buckling; the compressive rigidity of this zone is sufficient to undergo only deformations of small amplitude and therefore limited heating;
• a second annular zone, disposed on the outside of the vehicle, comprising the transverse recesses open on the side of the annular body; this zone is notably more flexible than the previous one and thus allows the maintenance of a large contact zone without blistering between the top of the support and the radially inner surface of the top of the tire and thus provides a large contact area between the ground and the surface of the tread of the tire during rolling in support by opposing any blistering of this tread.

In the previous paragraph, blistering means that the contact area between, for example the surface of the tread and the ground, is not continuous but on the contrary includes zones of interruption between the entry and the exit of this contact area. In these interrupted areas, there is an uplift of the tread which is no longer in contact with the ground. This phenomenon is due to longitudinal compression forces exerted on the top of the tire when laid flat in the contact area and the blistering results from the low compressibility of the top of the tire. The same phenomenon exists for supports. In the case of the support of the invention, it is the longitudinal compressibility of the flexible top around the hollowed out area linked to the chosen geometry and to the flexible elastomeric material which eliminates these blisters.

It is a decisive advantage of the safety support according to the invention that the flexibility from the top of the support allows its progressive support against the wall radially internal of the top of the tire with regular contact pressures and without blistering. Consequently, as we have seen, the contact area between the tire tread and the ground remains important too, with reduced risk of blistering of the tread and therefore with pressures of homogeneous contact. A blistering of this tread causes immediately a very inhomogeneous distribution of contact pressures and so very degraded behavior of the vehicle, especially when cornering.

When driving in a turn, the tires most in demand are those located on the outside of the turn. It is these tires which support the load the higher due to centrifugal forces. They also often have a camber marked, i.e. their mean longitudinal plane is not arranged perpendicular to the ground, but is also inclined towards the outside of the turn. All of this results in greater stress on the tread of the tires on the outward side of the turn. When rolling in support, this phenomenon is also very marked.

However, as the tires placed inside the turn are significantly less in demand, there is no need to have a provision symmetrical of the safety support according to the invention, this makes it possible to limit the necessary width of the support as well as its weight.

The transverse recesses also allow efficient ventilation of the support which limits its heating to admissible temperatures.

This combination ensures excellent vehicle behavior with at least a tire in support since this behavior is hardly modified by this support. This combination also gives exceptional endurance since the applicant has observed that it is possible to carry out pressure of zero inflation, several hundred kilometers at speeds of the order of 100 km / h.

According to an advantageous variant, the walls defined between two recesses adjacent are arched. These walls thus flex very gradually in the event of radial load with bending deformations. This avoids all buckling phenomenon which could cause discontinuity marked when pressed.

The particular geometry of the previous recesses makes it possible to use advantageously flexible elastomeric materials of shore A hardness less than 70, and preferably between 60 and 70.

In certain applications, it may also be advantageous to also carry out recesses opening on the side intended to be placed inside the vehicle. These recesses then have a substantially axial extension significantly less than those opening on the opposite side intended to be placed outside the vehicle.

• la figure 1 présente une demi-coupe axiale d'un appui de sécurité selon l'invention monté sur une jante préférentielle à l'intérieur de la cavité d'un pneumatique ;
• la figure 2 est une demi-coupe similaire à celle de la figure 1 dans laquelle l'appui de sécurité est en appui ;
• la figure 3 est une vue latérale partielle de l'appui de sécurité de la figure 1, du côté des évidements ;
• la figure 4 présente, en demi-coupe axiale, un second mode de réalisation d'un appui selon l'invention ; et.
• la figure 5 est une vue illustrant la déformation imposée à un appui lors de son introduction dans la cavité d'un pneumatique.

An embodiment of the invention is now presented without implied limitation with the aid of the appended drawing in which:

• FIG. 1 shows an axial half-section of a safety support according to the invention mounted on a preferential rim inside the cavity of a tire;
• Figure 2 is a half-section similar to that of Figure 1 in which the safety support is supported;
• Figure 3 is a partial side view of the safety support of Figure 1, on the side of the recesses;
• Figure 4 shows, in axial half-section, a second embodiment of a support according to the invention; and.
• FIG. 5 is a view illustrating the deformation imposed on a support when it is introduced into the cavity of a tire.

Figure 1 shows a safety support 1 according to the invention mounted around a preferential rim 2 and inside the cavity 30 of a tire 3 corresponding. This exemplary embodiment is dimensioned for the equipment of a small passenger vehicle like a Renault Twingo. The dimension of tire 3 is 145 x 360 where 145 corresponds to the width of the tire in millimeters and 360 to the diameter of rim 2 always in millimeters.

• un premier siège 21',
• une zone cylindrique plane 22 destinée à recevoir l'appui de sécurité 1 selon l'invention, le diamètre de cette zone 22 est supérieur à celui du siège 21' pour permettre un montage direct aisé de l'appui de sécurité par enfilage axial,
• une butée 23 de blocage transversal de l'appui,
• une gorge de montage 24, cette gorge 24 est de taille minimisée relativement aux gorges classiques de montage,
• un second siège 21" précédé d'un bossage de retenue 25, le diamètre de ce second siège est supérieur au diamètre de la zone 22. Une caractéristique de cette jante est que les deux sièges 21' et 21'' ont une pente inversée relativement aux sièges des jantes usuelles.

Rim 2 is part of a one-piece wheel. This rim 2 comprises axially, starting from the side of the disc 20 of the wheel, or from the side intended to be placed outside the vehicle:

• a first seat 21 ',
• a flat cylindrical area 22 intended to receive the safety support 1 according to the invention, the diameter of this area 22 is greater than that of the seat 21 ′ to allow easy direct mounting of the safety support by axial threading,
• a stop 23 for transversely blocking the support,
• a mounting groove 24, this groove 24 is of minimized size relative to conventional mounting grooves,
• a second seat 21 "preceded by a retaining boss 25, the diameter of this second seat is greater than the diameter of the zone 22. A characteristic of this rim is that the two seats 21 'and 21''have a relatively inverted slope to the seats of the usual rims.

The tire 3 is designed to be mounted on the rim 2 and comprises in in particular two beads 31 'and 31 "of different diameters.

a) une base 10, de forme généralement annulaire et renforcée par une nappe 11 orientée longitudinalement sensiblement à 0°;

b) un sommet 12, sensiblement annulaire, avec sur sa paroi radialement extérieure des rainures longitudinales 13 ;

c) un corps annulaire 14 de liaison entre la base 10 et le sommet 12.

Support 1 has three main parts:

a) a base 10, of generally annular shape and reinforced by a ply 11 oriented longitudinally substantially at 0 °;

b) a vertex 12, substantially annular, with on its radially outer wall longitudinal grooves 13;

c) an annular body 14 for connection between the base 10 and the top 12.

The section of FIG. 1 shows a first massive part 141 of the body 14 thus that a second part 142 comprising recesses 143 extending axially on substantially more than half of the body 14 opening onto the outside in a substantially axial direction. These recesses 143 are (FIG. 3) regularly distributed over the entire circumference of the body 14 and define radial walls 144 which provide a direct radial connection between the apex 12 and the base 10 of the support 1. The walls 144 have an arcuate shape. This geometry has the advantage of stressing in bending and not in compression these axial walls 144 when they are overwritten. The recesses 143 and therefore the walls 144 are enough to provide regular support when rolling under support.

The recesses 143 make it possible to very significantly reduce the weight of support 1. By way of example, in the preferred embodiment illustrated in the figures 1 to 3, with walls 144 7 mm thick, for a pitch of the pattern of 19 mm, extending over 70% of the axial width of the support, the weight only represents 67% of the weight of the corresponding full support.

The radial walls 144 are oriented axially in this embodiment. They can also deviate by up to 30 degrees from this axial orientation. The increase in the angle of inclination relative to the axial direction increases the radial stiffness of the support while retaining the other parameters of geometry and rigidity of identical materials. Beyond 30 degrees, the increase in rigidity is too high.

The elastomeric material chosen in this embodiment has a hardness shore A from 60 to 70. The radial rigidity of the part of the support 1 including the massive part 141 is of the order of 420 kg / cm and the radial rigidity of the part including the hollow part 142 is 160 kg / cm. As a result, 70% of the load is carried by the full part and 30% by the part comprising the recesses.

In this example, the base 10 of the support is reinforced with a ply 11 substantially oriented at zero degrees. This ply 11 is preferably composed of a reinforcement high modulus circumferential to guarantee almost non-extensibility circumferential of the support and therefore its maintenance on the rim 2 whatever the tire rotation speed. This sheet also has a low rigidity of bending to allow a significant deformation necessary for the introduction of the support in the tire before the actual threading of the support and the pneumatic when mounted on the rim 2.

In this embodiment, the base comprises a cylindrical stop 15 intended to lock in position the adjacent bead 31 'of the tire 3. The second bead 31 "is blocked by the usual boss 25.

The height of the safety support is chosen so as not to cause contact during all normal uses of the tire, even with notable momentary overloads. This height corresponds substantially to the half the height of the toroidal cavity 30 between the rim and the top of the pneumatic.

Preferably, one chooses as material constituting the support a material to base of an elastomer with saturated chains, such as EPDM.

To improve the endurance performance of the support, we usually include in the cavity 30 of the tire 3, a lubricant to lubricate the possible contact between the top of the support and the top of the tire.

Such a safety support 1 can be produced in the usual way by injection into a mold for example.

To assemble the assembly presented in figure 1, one begins by introducing the safety support 1 in the toric cavity 30 of the tire 3. A first part of the support in this cavity of the tire. Then, we switch (see Figure 5) axially outside the mean longitudinal plane of the support 1, the opposite part of the support so that it can enter the opposite part tire. The fact that the support is essentially made of a material flexible elastomer obviously facilitates this tilting that it is quite possible to perform manually without using any tool. We then introduce the tire assembly and support around the rim, starting with the bead 31 "of the tire 3 of larger diameter. This bead is placed 31 "in the mounting groove 24 and at the same time, the support 1 is put in place around the zone 22 of the rim 2. Then, the first bead 31 "is passed beyond of the boss 25 and beyond the seat 21 "thanks to the mounting groove 24. On mount this first bead 31 '' on its seat 21 "from the outside, finally we mount the second bead 31 'of the tire 3 of small diameter on its seat 21' also at from outside this seat.

In FIG. 2, we see a safety assembly similar to that of FIG. 1 in operation. The top 12 of the support 1 is in contact with the surface radially inside the top of the tire 3.

A critical point in the design of a support 1 is the determination of the axial width of the annular solid part 141. The axial width is defined relative of this massive annular part 141 as the ratio between the width axial of this massive annular part and the total axial width of the support. As example, for a relative axial width of 5%, the life of the support with a RENAULT brand passenger vehicle, Twingo model was 150 kilometers when driving at full load, at 100 km / h and with a pressure of no inflation. But, from a width of 15%, the lifespan in the same test conditions exceeded 600 kilometers. Of course, an increase later the width of the massive part increases the weight and decreases the support ventilation. It is therefore necessary to determine the dimensions and the most appropriate rigidities depending on the vehicles to be fitted.

A safety support 1 according to the invention can also, of course, be mounted on a standard two-part rim with a flat rim tape.

• un anneau 51 de section axiale sensiblement rectangulaire ; et
• un ou plusieurs éléments annulaires 52, ici deux, présentant une pluralité d'évidements 53 s'étendant sensiblement axialement sur toutes leurs largeurs et sensiblement régulièrement répartis sur leurs circonférences ;

ces éléments annulaires 52 sont destinés à être disposés sur la jante 2, relativement à l'anneau 51 du côté destiné à être placé vers l'extérieur du véhicule. Comme précédemment, chaque élément annulaire 51 et 52 comprend un sommet 12 destiné à venir en appui contre la surface radialement intérieure du sommet du pneumatique et une base 10 destiné à être en contact avec une jante 2. Les bases 10 comprennent un élément de renfort longitudinal 11 pour garantir une quasi-inextensibilité longitudinale.According to a second embodiment presented in FIG. 4, the safety support 5 consists of several rings:

• a ring 51 of substantially rectangular axial section; and
• one or more annular elements 52, here two, having a plurality of recesses 53 extending substantially axially over all their widths and substantially regularly distributed over their circumferences;

these annular elements 52 are intended to be arranged on the rim 2, relative to the ring 51 on the side intended to be placed towards the outside of the vehicle. As before, each annular element 51 and 52 comprises a crown 12 intended to come into abutment against the radially inner surface of the crown of the tire and a base 10 intended to be in contact with a rim 2. The bases 10 comprise a longitudinal reinforcing element 11 to guarantee a longitudinal quasi-inextensibility.

This second embodiment has properties very close to the first but is easier to introduce into a tire due to the stiffness in lower bending of its different annular elements.

Claims (10)

1. A safety support (1, 5) intended to be mounted on a rim (2) on the inside of a tyre (3) fitted on a vehicle, to support the tread of this tyre (3) in the event of a loss of inflation pressure, said support (1, 5) being essentially made of a flexible elastomeric material, and comprising:

   a substantially cylindrical base (10) intended to be adapted around the rim (2),

   a substantially cylindrical crown (12) intended to come into contact with the tread in the event of a loss of pressure, and leaving a clearance relative to the latter at rated pressure, and

   an annular body (14) connecting said base (10) and said crown (12),

   said support being characterised in that said body (14) has a plurality of cutouts (143, 53) of substantially axial direction, opening into that face of the body which is intended to be placed on the outside of the vehicle and extending axially as far as at least half of said body (14) without passing right through it.
2. A support (1, 5) according to Claim 1, in which the annular body (14) has the same axial width as the base (10).
3. A support (1, 5) according to one of Claims 1 or 2, in which the adjacent cutouts (143, 53) are separated by arched walls (144).
4. A support (1, 5) according to one of Claims 1 to 3, in which the cutouts (143, 53) extend at a direction less than 30 degrees relative to the axial direction.
5. A support (1, 5) according to one of Claims 1 to 4, in which the flexible elastomeric material has a Shore A hardness less than 70 and preferably between 60 and 70.
6. A support (1, 5) according to one of Claims 1 to 5, in which the flexible elastomeric material is based on an elastomer having saturated chains.
7. A support (1, 5) according to one of Claims 1 to 6, in which the base (10) comprises substantially inextensible longitudinal reinforcement means (11).
8. A support (1, 5) according to one of Claims 1 to 7, in which the crown (12) comprises circumferential grooves (13) on its radially outer surface.
9. A support (1, 5) according to one of Claims 1 to 8, in which the annular body (14) furthermore has a plurality of cutouts of substantially axial direction, opening into that face of the body which is intended to be placed on the inside of the vehicle.
10. A support (5) according to one of Claims 1 to 9, made of at least two independent annular pieces (51, 52) intended to be arranged side by side around the rim (2).

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